Right now I could buy the entire AJE pack at an excellent 50% discount. Great Value!! However if you already own the base game and a couple of the expansions there is not discount on the remaining expansions. I just want Parthian Wars and Hannibal but they come to nearly twice as much as the complete version on sale.

Why aren't the DLCs on sale as well?

The only option I can think off is to purchase the whole pack to get those 2 DLC. Why not just put a discount on the DLC as well?